1. Field of the Invention
The present invention relates to 9-dihydro-9-O-alkyldesmycosin derivatives and salts thereof which are useful as an antimicrobial agent.
2. Description of the Background
Desmycosins (4'-demycarosyltylosins) do not produce a sufficiently high blood concentration by oral administration, and are thus incapable of providing a satisfactory infection curing effect. Various desmycosin derivatives have been prepared in an effort to find compounds which do not have this problem. For example, a desmycosin derivative having an improved bioavalability such as an improved blood concentration was prepared by modifying the 20-position aldehyde group of desmycosin [J. Med. Chem., 31, 1631-1641 (1988)]. There have been no published reports, however, dealing with modification of groups other than the aldehyde group in order to improve the in vivo efficiency of desmycosin. There is thus a strong desire for the development of a novel desmycosin derivative which can exhibit a satisfactory infection curing effect by oral administration.
In view of this situation, the present inventors have undertaken extensive studies concerning desmycosin derivatives. As a result the inventors found that 9-dihydro-9-O-alkyldesmycosin derivatives having a satisfactory infection curing effect by oral administration can be prepared by modifying the oxygen functional group bonding to position 9 of desmycosin. This finding has led to the completion of the present invention.